When yo red breastfeeding

Honestly science doesn't have a set answer so it just depends on when you're ready. Some studies say wait 4 hours, some say wait 7 days, some say it's not enough in the milk to even get into the babies system so you can do it right after. (Most of these studies are too small scale to be a proven fact) There's just not enough research to definitively say.

1 instance of smoking can stay in your body a week! You can get home test strips but only use them with urine- testing breast milk will cause false negatives because they aren't made for that.